1. Field of the Invention
The present invention relates to a mechanism for controlling the position of an optical element which is moved in an optical axis direction in an optical apparatus.
2. Description of the Related Art
In optical apparatuses such as cameras, a mechanism in which a guide shaft is inserted into a guide hole to be freely slidable relative to the guide hole with the lengthwise direction of the guide shaft being parallel to an optical axis, and another mechanism wherein a guide projection is engaged in a guide groove to be freely slidable relative to the guide groove with the lengthwise direction of the guide groove being parallel to an optical axis, are known in the art as an advancing/retracting movement guide mechanism for moving an optical element holding member which supports an optical element such as a lens group in an optical axis direction. The former type of guide mechanism which includes the guide shaft and the guide hole is disclosed in, e.g., Japanese Unexamined Patent Publication 2000-206391.
In aforementioned type of guide mechanisms, at each of the slidable portions between the guide hole and the guide shaft and between the guide groove and the guide projection, a predetermined clearance is created to make relative sliding movement possible. Furthermore, measures are taken to eliminate backlash to prevent rattle and noise which may be caused by the clearance and to make stable position-control possible.